package main // import "git.fromouter.space/mcg/htmlroc"
import (
	"flag"
	"fmt"
	"html/template"
	"io/ioutil"
	"os"
	"strings"
)

// Where are we in the file
const (
	FStart   = "start"    // File start
	InTOC    = "intoc"    // In Table of content
	AfterTOC = "aftertoc" // After Table of content
)

// TemplateData is the data that is filled and passed to the HTML template
type TemplateData struct {
	Title   string
	CSSFile string
	Credits string
}

var funmap = template.FuncMap{
	"htmlify": tplHtmlify,
}

// HTMLrocCredits is the credit string to append to the other credits
const HTMLrocCredits = "Converted to HTML using <a href=\"https://git.fromouter.space/mcg/htmlroc\">htmlroc</a>"

func main() {
	txtfile := flag.String("in", "rules.txt", "Path to rules.txt file")
	tplfile := flag.String("template", "template.html", "Path to template file")
	outname := flag.String("out", "out.html", "Output file")
	style := flag.String("css", "style.css", "Name of the CSS stylesheet")

	// Read template file
	tpl, err := template.New(*tplfile).Funcs(funmap).ParseFiles(*tplfile)
	checkErr(err, "Could not load template file \"%s\"", *tplfile)

	tpldata := TemplateData{
		CSSFile: *style,
	}

	// Read rules file
	filebytes, err := ioutil.ReadFile(*txtfile)
	checkErr(err, "Could not read rules file \"%s\"", *txtfile)

	filestr := string(filebytes)

	// Use table of content as delimiter between credits and rule text
	toc := strings.Index(filestr, "Table of Contents")
	if toc < 0 {
		fmt.Fprintln(os.Stderr, "could not find TOC")
		os.Exit(1)
	}

	// Extract credits
	tpldata.Credits, filestr = strings.TrimSpace(filestr[:toc]), filestr[toc:]

	// Add our own credits
	tpldata.Credits += "\n" + HTMLrocCredits

	// Rules are after TOC
	tocend := strings.Index(filestr, "\n\n")
	if tocend < 0 {
		fmt.Fprintln(os.Stderr, "could not find end of TOC")
		os.Exit(1)
	}

	// Strip TOC out
	filestr = filestr[tocend+2:]

	// Every rule is a line (pretty handy!)
	lines := strings.Split(filestr, "\n")
	for _, line := range lines {
		// Skip empty lines
		line = strings.TrimSpace(line)
		if len(line) < 1 {
			continue
		}
	}

	// Create output file
	outfile, err := os.Create(*outname)
	checkErr(err, "Could not create output file \"%s\"", *outname)
	defer outfile.Close()

	// Run template on output file stream
	checkErr(tpl.Execute(outfile, tpldata), "Error running template")
}

func checkErr(err error, fmtstr string, args ...interface{}) {
	if err != nil {
		fmt.Fprintf(os.Stderr, "FATAL: "+fmtstr+":\n  ", args...)
		fmt.Fprintln(os.Stderr, err.Error())
		os.Exit(1)
	}
}

func tplHtmlify(str string) template.HTML {
	// Make first line an heading
	idx := strings.IndexRune(str, '\n')
	if idx > 0 {
		str = "<h1>" + str[:idx] + "</h1>" + str[idx:]
	}
	// Replace newlines with HTML line-break tag
	str = strings.ReplaceAll(str, "\n", "<br />")
	return template.HTML(str)
}